Comparative Analysis of Three Guinea Pig Satellite DNAs by Restriction Nucleases

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Abstract
The structures of guinea pig satellite DNA I, II and III were analyzed by digestion with 7 restriction nucleases. From the cleavage patterns it is obvious that the long-range periodicities in these 3 satellites differ rather characteristically. Satellite I is fairly resistant to 6 nucleases and gives only a number of weak discrete bands which do not show a simple regularity. But it is cleaved extensively by the restriction nuclease from Arthrobacter luteus and yields very heterogeneous breakdown products. This is consistent with the high extent of divergence previously found for this satellite, e.g., by sequence analysis. Satellite II is almost completely resistant to all nucleases, indicative of a high degree of sequence homogeneity of this satellite. Satellite III is completely broken by the restriction nuclease from Bacillus subtilis into fragments which form a novel, highly regular series of bands in gel electrophoresis. The patterns show that the satellite is composed of tandem repeats of approximately 215 nucleotide pairs length, each repeat unit containing 2 cleavage sites for this nuclease. The data are consistent with the assumption that 30-40% of all cleavage sites were eliminated by a random process. Satellite III DNA yields weak degradation patterns of the same periodicity with a number of other restriction nucleases. Cleavage sites for these nucleases are clustered on separate small segments of the satellite DNA. In this respect, the satellite is similar to others, notably the mouse satellite DNA. The 3 guinea pig satellites are examples of more general types of satellite structures also found in other organisms. Similarities and differences to other satellites are discussed with special consideration to theories on the evolution of this class of DNA.